Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $72.95   3.577%   $75.5594   $75.56   $75.55   $75.60  
  Purchase #2 $84.36   9.207%   $92.127   $92.13   $92.15   $92.10  
  Purchase #3 $90.71   3.461%   $93.8495   $93.85   $93.85   $93.80  
  Purchase #4 $51.77   12.365%   $58.1714   $58.17   $58.15   $58.20  
  Purchase #5 $177.29   6.320%   $188.4947   $188.49   $188.50   $188.50  
  Purchase #6 $177.56   13.175%   $200.9535   $200.95   $200.95   $201.00  
  Purchase #7 $42.53   12.563%   $47.873   $47.87   $47.85   $47.90  
  7 purchase totals = $697.17       $757.0285   $757.02   $757.00   $757.10